Hygrometer, humidity regulator, and the like



Jul 1 I927.

y A. J. LOEPSINGER HYGROMETER, HUMIDITY REGULATOR, AND THE LIKE Filed Aug. 22. 1924 INVENTOR a 5 661 51 Loepszlu r BY W Mug (Mr- ATTORNEY Patented July 19, 1927.

UNITED sTATEs I 1,636,374 PATENT OFFICE.

ALBERT J. LOEPSINGER, OF PROVIDENCE, RHODE ISLAND, ASSIGNQR' T GENERAL FIRE EXTINGUISHER COMIANY, OF PROVIDENCE, RHODE ISLAND, A CORPORA- TION OF DELAWARE.

HYGBOMETER, HUMIDITY REGULATOR, AND THE LIKE.

Application filed August 22, 1924. Serial No. 733,537.

This invention relates to improvements in hygrometers, humidity regulators and the like. More especially it relates to an 1m proved method of affecting the action of the wet-bulb element of such devices, and to apparatus by which the method may be practiced.

It is customary to create a wet bulb depression by evaporation of moisture either directly at the surface of the wet bulb element, as by a wick. or in the immediate vicinity of the bulb, as in the cases where a super-saturated current of air is directed against it. Both of these particular methods are objectionable, as is also any other whlch depends upon a wet surface, because such surface collects foreign matter from the surrounding air, It is to the elimination of the troubles and inaccuracies characteristic of the performance of wetted wet bulb elements that the present invention is directed.

Among the features of the invention is the subjecting of the wet bulb element to a bath of saturated air having proper. wet bulb ten'i 'ierature but no moisture in liquid form. Another feature resides in the means for producing the temperature of this air, that is, in the provision of a porous body charged interiorly with moisture, whose tangible surfaces remain ostensibly dry, and yet give up moisture for evaporation by the air passed over them through such a long path that the air becomes saturated and cooled to the proper degree.

These objects are attained by providing a passage with evaporative walls, through which is slowly passed a mild current of the air whose humidity is to be indicated. Such a passage may be formed in several ways, but the particular means disclosed herein comprises a succession of tubular containers of porous and capillary ceramic material mounted one within another upstanding in a pan of water. Air whose humidity is to be indicated is forced into the upper portion of the inmost tube, thence flows downward along its surface and out through openings in its lower part into the annular chamber formed between it and the next. It is preferable that the material employed be such that the exterior tangible surfaces of the porous material feel dry, while its interior cells contain moisture that has been fed upward from the pan by the capillary power of the ceramic material. The evaporation of this moisture into the passing air saturates that air, the passage preferably being made long enough and the flow of air small enough so that this result is attained. During this transition period the temperature of the air will fall, according to the degree of evaporation which occurs, by an amount which represents the wet bulb depression. From this cooling chamber the air passes directly to the thermally responsive wet bulb element, to which it imparts its own temperature. No deposit of moisture on the element occurs, because there is no excess moisture in the air, consequently the surface of the wet bulb element continues dry, with no accumulation of foreign particles. Thus this element is always ready to respond instantly to changes in the air flowing past it, and. gives indications or re ulation accurately and in conformity with the actual humidity conditions of the atmosphere which controls it.

It is intended that the patent shall cover. by suitable expression in the appended claims, whatever features of patentable novelty exist in the invention disclosed.

In the accompanying drawing:

The figure is an elevation of a humidity controller, embodying apparatus shown largely in medial section, having the characteristics of the invention and by which the invention may be practiced.

Referring to the drawing the apparatus illustrated comprises two upstanding containers 10 and 19. which conveniently are tubular and of suitable dimension to be arranged one with-in the other, upstanding in a pan of water 14. These tubes are preferably made of insoluble porous earthy material, having a capillary power sufiicient to fill their walls with moisture, for evaporation into the air which passes through them. This air is preferably introduced into the upper closed part of the hollow of the inner container, under light pressure, through an entrance pipe 16, which as illustrated extends up through the pan 14 into the tube. The air circulates downward within the tube. taking up moisture from the inner surface of its walls, passes through holes 18 near the bottom, just above the water level, into the annular passage 20 between it and the next outer container where it flows upward along similar evaporative walls. The top of this container 12 has an outlet 22 leading directly to the bulb 24 of a wet bulb thermometer, or to whatever other thermally responsive element is to be subjected to wet, bulb temperature. The passage 22 may be formed in such shape and size as is suitable to permit the air to control the temperature of this element.

In the illustrated application of the invention the outlet 22 is covered with a heat insulating jacket and is extended and shaped to enclose both the bulb 24 of the wet bulb thermometer and a thermally responsive or wet bulb element 26 of a humidity controllers While any type of controller may be employed, the type chosen for illustration is one embodying well known principles which are more particularly disclosed in United States Patent N 0. 1,032,189, granted July 9, 1912. In this, which is indicated in diagram only, the operation of humidifying apparatus (not shown) is controlled by air pressure conveyed by suitable small pipe connections (not shown) governed by a valve 28 Whose opening and closing are effected by a lever 30 connected with a diaphragm of a relay valve 32, whose movements depend upon air admitted and released through a ratio valve within the covering 34. This ratio valve in turn is actuated by the relative or co-operative effect of the expansions and contractions of the dry bulb element 36 and the wet bulb element 26, the former being responsive only to temperature changes in the atmosphere and the latter being influenced by the temperature of the cooled air which circulates around and along it in the passage provided by the extended outlet 22 from the container 12. A

suitable discharge passage 22 is provided at the end of this outlet extension, having a damper 38, or valve of the butterfly type, by which the velocity of the air flowing through the cooling tubes may be regulated. Preferably a light pressure blower 40 is employed to insure ample circulation of air through the tubes 10 and 12, the blower being of a type such as a Ian, so that closure of the damper 38 merely causes less air to be passed through the blower.

As atmospheric air having the relative humidity which is to be detected leaves the entrance pipe 16 and passes over the surfaces of the capillary and porous walled containers, it is subjected to temperature change in that the moisture in the containers evaporates into it, cooling the surroundings,--walls and air. The total of passages should be long enough for the air in them to be cooled to a temperature corresponding to wet bulb depression by the time it arrives at the Wet bulb element; and the size of the passage should be large enough' for the evaporation which occurs to control the temperature of air and walls.

The apparatus thus shows the bringing of a thermally responsive element to wet bulb temperature without wetting that element. It may be varied in design and construction. A large number of containers may be employed, in which case, the inner will be more thoroughly insulated from temperature modification by the surrounding atmosphere and 'more completely under control of the incoming sample thereof which is depressed in temperature by the evaporation into it. The said sample may be introduced by a small power fan (as at 40,) or by other suitable means, continuously or intermittently operatin The ceramic material referred to may be crystalline alumina of the type produced by electric furnace and known in the trade as alundum or refractory alumina. Experiments with one of the coarsest commercial grades of this, as made for filtering devices, known commercially as having porosity R A 98, have given satisfactory results. Owing to its porosity this filtering material has capillary power to raise water; and owing to its earthy nature it is insoluble, rigid,

and may be sufliciently strong and thick to be satisfactorily resistant to fracture.

One arrangement employing a. larger number of containers is indicated in the drawing, where the outside container 42 is a mere protective shield.

The number of these containers may vary in practice and will be affected by their height, the breadth of passage between them, and the rate of flow of air. In general, any conditions of height, length and breadth of passage or rate of flow having been assumed, the others of these conditions can be determined by experiment. It is to be observed however, that it is not necessary for the practical success of the apparatus, that the air flowing to the wet bulb element should have been actually cooled to the full wet bulb depression, nor that the air shall have become fully saturated, for it has been found that if these conditions are approximately attained a proportional effect is had on the wet bulb element, and the apparatus can be adjusted so that such a proportional effect is practically effective, varying as it does with the theoretical full wet bulb depression. And there is indeed a certain advantage in having this air a trifle short of complete saturation, for a situation is threoretically possible in which by a rise of temperature in air of humidity there might be some condensation on the then cooler wet bulb element; in which case the air, assumed to be fully saturated. could not evaporate the deposited water. and the bulb might under these special circunr stances remain wet for a period. But if the air were not fully saturated this situation would soon be corrected if it should arise. It will be seen thus that the air may be at a is not necessarily the same as the wet bulb temperature that might be shown by a psy-' chrometer, provided that it is some temperature corresponding to such wet bulb temperature.

I claim as my invention:

1. The method of producing a temperature approximating wet bulb temperature, in a thermally responsive element, comprising the causing of a stream of sample airto move over a supply of moisture, whence by e 'aporation the air picks up moisture and becomes cooled to the temperature corresponding to wet bulb depression, and then directing said air at said temperature over the said element thereby transmitting said temperature thereto; meanwhile maintaining said air free from sensible moisture.

2. The method of producing a temperature approximating wet bulb temperature, in a thermally responsive element, comprising causing a stream of air to move over the surface of a body containing water evapo rating into the said air, whereby the air becomes cooled to the temperature corresponding to wet bulb depression without acquiring water in liquid form; and then at such temperature directing the cooled air over the said element.

3. The method of setting the temperature of a thermally responsive element, comprising the causing of a stream of air free from sensible moisture to pass over the element in such manner as to transmit its temperature thereto; and preliminarily cooling the stream to temperature corresponding to wet bulb temperature; the said wet bulb temperature being initially attained by evaporating water, to the extent of the moisture absorbing capacity of the air, into a sample constantly drawn from that air to which the wet bulb depression relates.

4. The method of producing a temperature approximating wet bulb temperature in a thermally responsive element, comprising the causing of a stream of air to move through a compartment containing water unasso ciated with the said element and having a freely evaporating surface, whereby by absorbing evaporation from said surface the air becomes cooled to a temperature corresponding to wet bulb depression and thereafter transmitting the ten'iperature of the air thus cooled to the said element and mean- \vhilemiaintaining the said element dry.

5. Apparatus for producing wet bulb temperature in a thermally responsive element, comprising, said element, a tubular container having an evaporative wall: means for moving air in a current through the container;

means for supplying moistureto said wall, whereby air that may be moved in a current along it contacts with the wall and the moisture therein and is thereby cooled to the temperature which corresponds to wet bulb depression; there being means for directing said cooled air at said temperature from the container upon the said element.

6. Apparatus for producing wet bulb temperature in a thermally responsive element, comprising, said element, a water basin, a plurality of tubular containers of capillary evaporative material arranged one within the other and upstanding from the water in said basin, the inner container having an opening into the annular chamber between the containers; means for moving a current of air along theevaporative walls of the inner container, said opening, and the annular chamber, and thence upon the said element; the said air in its passage evaporating moisture from the walls and being cooled to the temperature corresponding to wet bulb depression, whereby the said element is brought to said temperature.

7. Apparatus for producing wet bulb temperature in a thermally responsive element, comprising, said element, walls containing moisture and constituting an evaporative passage, and means for directing a current of air along said passage and into contact with said element; the said passage being long enough for the air passing therethrough to evaporate sufficient moisture from said walls to cool them and it to a temperature corresponding to wet bulb depres-' sion, whereby its contact with said element produces said temperature in the latter.

8. Apparatus for producing wet bulb temperature in a thermally responsive element, comprising, said element, walls constituting a passage leading thereto, means for moving air along said passage and into contact with the element, and means associated with said passage for producing Wet bulb temperature in the air without sensible moisture therein; the exterior surface of said walls being dry whereby the passing air is maintained free from sensible moisture.

9. Apparatus for producing wet bulb tem-- perature in a thermally responsive element, comprising, said element, walls constituting a passage leading thereto, means for moving air along said passage and into contact with the element, and means associated with said passage in advance of the element for producing wet bulb temperature in the air without sensible moisture therein; the exterior surface of said walls being dry whereby the passing air is maintained tree from sensible moisture, and means for regulating the flow of air through the passage.

Signed at Boston, Massachusetts, this nineteenth day of June, 1924..

ALBERT J. LOEPSINGER. 

